Intense research has been conducted on jellyfish and ctenophores in recent years. They are increasingly recognized as key
elements in the marine ecosystem that serve as critical indicators and drivers of ecosystem performance and change.
However, the bacterial community associated with ctenophores is still poorly investigated. Based on automated ribosomal
intergenic spacer analysis (ARISA) and 16S ribosomal RNA gene amplicon pyrosequencing, we investigated bacterial
communities associated with the frequently occurring ctenophore species Mnemiopsis leidyi, Beroe sp., Bolinopsis infundibulum
and Pleurobrachia pileus at Helgoland Roads in the German Bight (North Sea). We observed significant differences between
the associated bacterial communities of the different ctenophore species based on ARISA patterns.With respect to bacterial
taxa, all ctenophore species were dominated by Proteobacteria as revealed by pyrosequencing. Mnemiopsis leidyi and P. pileus
mainly harboured Gammaproteobacteria, with Marinomonas as the dominant phylotype of M. leidyi. By contrast,
Pseudoalteromonas and Psychrobacter were the most abundant Gammaproteobacteria in P. pileus. Beroe sp. was mainly
dominated by Alphaproteobacteria, particularly by the genus Thalassospira. For B. infundibulum, the bacterial community
was composed of Alphaproteobacteria and Gammaproteobacteria in equal parts, which consisted of the genera
Thalassospira and Marinomonas. In addition, the bacterial communities associated with M. leidyi display a clear variation over
time that needs further investigation. Our results indicate that the bacterial communities associated with ctenophores are
highly species- specific.